Wireless power storage device, semiconductor device including the wireless power storage device, and method for operating the same

ABSTRACT

To simplify charging of a battery in a power storage device which includes the battery. Further, to provide a wireless power storage device which can transmit and receive information without the task of replacing a battery for drive power supply, which becomes necessary when the battery depletes over time, being performed. An antenna circuit, a battery which is electrically connected to the antenna circuit via a rectifier circuit, and a load portion which is electrically connected to the battery are provided. The battery is charged when an electromagnetic wave received by the antenna circuit is input to the battery via the rectifier circuit, and discharged when electrical power which has been charged is supplied to the load portion. The battery is charged cumulatively, and the battery is discharged in pulses.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a wireless power storage device and asemiconductor device including the wireless power storage device. Inparticular, the invention relates to a wireless power storage devicewhich transmits and receives data through electromagnetic waves andreceives electrical power through electromagnetic waves, and to asemiconductor device including the same.

2. Description of the Related Art

In recent years, various electric appliances are coming into wide use,and a wide variety of products are being put on the market. Inparticular, the spread of portable wireless communication devices hasbeen notable. As a power supply for driving a portable wirelesscommunication device, a battery, which is a power receiving means, isbuilt-in, and power is obtained from the battery. As a battery, asecondary cell such as a lithium ion battery or the like is used. Asmatters now stand, the battery is charged from an AC adaptor which isplugged into a household alternating current power supply, which is apower supply means (for example, see Reference 1: Japanese PublishedPatent Application No. 2005-150022).

Further, in recent years, individual identification technology whichemploys wireless communication which uses an electromagnetic field,radio waves, or the like has attracted attention as a mode of usage ofwireless communication devices. In particular, an individualidentification technology which employs an RFID (radio frequencyidentification) tag that communicates data via wireless communication,which is an example of a wireless communication device, has attractedattention. An RFID tag is also referred to as an IC (integrated circuit)tag, an IC chip, an RF tag, a wireless tag, and an electronic tag.Individual identification technology which employs RFID tags isbeginning to be made use of in production, management, and the like ofindividual objects, and it is expected that this technology will also beapplied to personal authentication, through inclusion in cards or thelike.

RFID tags can be divided into two types, according to whether they havea built-in power supply or receive a power supply from outside: activetype RFID tags, which can transmit an electromagnetic wave whichcontains information included in the RFID tag, and passive type RFIDtags, which drive by converting an electromagnetic wave (a carrier wave)from outside into electrical power (regarding the active type, seeReference 2: Japanese Published Patent Application No. 2005-316724, andregarding the passive type, see Reference 3: Japanese Translation of PCTInternational Application No. 2006-503376). Active type RFID tags have abuilt-in power supply for driving the RFID tag, and include a battery asthe power supply. Meanwhile, with passive type RFID tags, a power supplyfor driving the RFID tag is made by employing electrical power of anelectromagnetic wave (a carrier wave) from outside. Passive type RFIDtags have a structure which does not include a battery.

SUMMARY OF THE INVENTION

However, the frequency of use of movable electronic devices has risensteadily, and there is a limit to improving the durability of batteriesand reducing power consumption in order to cope with the operating time.Further, for charging a battery which is a power supply built into amovable electronic device, there have not been any methods other thancharging from a charger through an AC adaptor via a householdalternating current power supply or charging from a commerciallyavailable primary battery. Therefore, there has been a problem in thatcharging has been troublesome for users, and it has been necessary forusers to take an AC adaptor or a primary battery which is a power supplymeans with them when they are moving about outdoors, which isburdensome.

In the case of an active type RFID tag which includes a battery fordriving, compared with a passive type RFID tag the communication rangecan be made longer; however, there have been problems such as the factthat the battery is used up over time in accordance with transmissionand reception of information and the intensity setting of anelectromagnetic wave necessary for transmitting and receiving, andeventually the electrical power necessary for transmitting and receivingthe information cannot be generated. Therefore, there has been a problemin that in order to keep using the active type RFID tag which includesthe battery for driving, the tasks of checking the remaining capacity ofthe battery and replacing the battery arise.

Therefore, an object of the present invention is to make charging abattery of a power storage device which includes the battery easier.Further, an object of the invention is to provide a wireless powerstorage device which can transmit and receive information without thetask of replacing a battery for drive power supply, which arises whenthe battery depletes over time, being performed, and to provide asemiconductor device which includes the wireless power storage device.

In order to solve the above problems, in a wireless power storage deviceof the invention, an RF battery (a wireless battery) which can becharged wirelessly by receiving an electromagnetic wave is provided.Further, the RF battery is charged over a long period of time, anddischarging of electricity is conducted for a shorter period of time (inpulses) than the period of time charging is conducted for. Specificstructures of the invention will be described below.

A wireless power storage device of the invention includes an antennacircuit, a battery which is electrically connected to the antennacircuit through a rectifier circuit, and a load portion which iselectrically connected to the battery. The battery is charged when anelectromagnetic wave received by the antenna circuit is input to thebattery through the rectifier circuit, and is discharged when thecharged electrical power is supplied to the load portion. The battery ischarged cumulatively and the battery is discharged in pulses. A loadportion refers to a circuit or the like which uses electrical power ofthe battery to operate.

A wireless power storage device of the invention includes an antennacircuit, a battery which is electrically connected to the antennacircuit through a rectifier circuit, and a load portion which iselectrically connected to the battery. The battery is charged when anelectromagnetic wave received by the antenna circuit is input to thebattery through the rectifier circuit, and is discharged when thecharged electrical power is supplied to the load portion. The period oftime that the battery is charged for is longer than the period of timethe battery is discharged for.

A wireless power storage device of the invention includes an antennacircuit, a battery which is electrically connected to the antennacircuit through a rectifier circuit and a charge control circuit, and aload portion which is electrically connected to the battery through adischarge control circuit which includes a switch. The battery ischarged when an electromagnetic wave received by the antenna circuit isinput to the battery through the rectifier circuit and the chargecontrol circuit, and is discharged when the charged electrical power issupplied to the load portion through the discharge control circuit. Thebattery is charged cumulatively, and is discharged in pulses when theswitch turns on in response to a voltage supplied from the battery tothe discharge control circuit.

A wireless power storage device of the invention includes an antennacircuit, a battery which is electrically connected to the antennacircuit through a rectifier circuit and a charge control circuit, and aload portion which is electrically connected to the battery through adischarge control circuit which includes a switch. The battery ischarged when an electromagnetic wave received by the antenna circuit isinput to the battery through the rectifier circuit and the chargecontrol circuit. The battery is discharged when the switch turns on inresponse to a voltage supplied from the battery to the discharge controlcircuit and thereby electrical power charged to the battery is suppliedto the load portion. The period of time that the battery is charged foris longer than the period of time that the battery is discharged for.

A wireless power storage device of the invention includes an antennacircuit, a battery which is electrically connected to the antennacircuit through a rectifier circuit and a charge control circuit, and aload portion which is electrically connected to the battery through adischarge control circuit which includes a first switch and a switchingcircuit which includes a second switch. The battery is charged when anelectromagnetic wave received by the antenna circuit is input to thebattery through the rectifier circuit and the charge control circuit,and is discharged when electrical power which has been charged issupplied to the load portion through the discharge control circuit andthe switching circuit. The battery is charged cumulatively. The batteryis discharged in pulses when the first switch turns on, in response to avoltage supplied from the battery to the discharge control circuit, andthe second switch turns on.

A wireless power storage device of the invention includes an antennacircuit, a battery which is electrically connected to the antennacircuit through a rectifier circuit and a charge control circuit, and aload portion which is electrically connected to the battery through adischarge control circuit which includes a first switch and a switchingcircuit which includes a second switch. The battery is charged when anelectromagnetic wave received by the antenna circuit is input to thebattery through the rectifier circuit and the charge control circuit.The battery is discharged when the first switch turns on, in response toa voltage supplied from the battery to the discharge control circuit,and the second switch turns on, so that electrical power which has beencharged to the battery is supplied to the load portion. The period oftime that the battery is charged for is longer than the period of timethat the battery is discharged for.

A wireless power storage device of the invention has an above-describedstructure, and on and off of the second switch are controlled at aconstant frequency.

A wireless power storage device of the invention has an above-describedstructure, and the amount of electrical power charged to the battery perunit time is less than the amount of electrical power discharged fromthe battery per unit time.

A semiconductor device of the invention includes an antenna circuit, anda power supply portion and a signal processing circuit which areelectrically connected to the antenna circuit. The power supply portionincludes a battery, which is electrically connected to the antennacircuit through a rectifier circuit and a charge control circuit, and adischarge control circuit which includes a switch. The signal processingcircuit performs communication of information with the outsidewirelessly through the antenna circuit. The battery is charged when anelectromagnetic wave received by the antenna circuit is input to thebattery through the rectifier circuit and the charge control circuit,and is discharged when electrical power which has been charged issupplied to the signal processing circuit. The battery is chargedcumulatively. The battery is discharged in pulses when the switch turnson in response to a voltage supplied from the battery to the dischargecontrol circuit.

A semiconductor device of the invention includes a first antennacircuit, a second antenna circuit, a power supply portion which iselectrically connected to the first antenna circuit, a signal processingcircuit which is electrically connected to the second antenna circuit,and a sensor portion which is connected to the power supply portion andthe signal processing circuit. The power supply portion includes abattery, which is electrically connected to the first antenna circuitthrough a rectifier circuit and a charge control circuit, and adischarge control circuit which includes a switch. The signal processingcircuit transmits and receives information to and from the outsidewirelessly via the second antenna circuit. The sensor portion iselectrically connected with the battery through the discharge controlcircuit. The battery is charged when an electromagnetic wave received bythe first antenna circuit is input to the battery through the rectifiercircuit and the charge control circuit. The battery is discharged whenelectrical power which has been charged is supplied to the sensorportion through the discharge control circuit. The battery is chargedcumulatively. The battery is discharged in pulses when the switch turnson in response to a voltage supplied from the battery to the dischargecontrol circuit.

A semiconductor device of the invention has an above structure, and afrequency of an electromagnetic wave that the first antenna circuitreceives is different to a frequency of an electromagnetic wave that thesecond antenna circuit receives.

A semiconductor device of the invention has an above structure, and theamount of electrical power charged to the battery per unit time is lessthan the amount of electrical power discharged from the battery per unittime.

In the invention, by providing a wireless power storage device with abattery capable of wireless charging, charging of the battery providedin the wireless power storage device is made easier, and a wirelesspower storage device that is capable of transmitting and receivinginformation to and from the outside, without the task of replacing thebattery due to depletion of the battery over time being performed, canbe provided. Further, when the battery is charged over a certain periodof time by receiving electromagnetic waves, and stored electrical poweris discharged in pulses, a large amount of electrical power can besupplied even when an electromagnetic wave used in charging the batteryis weak.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a structural example of a wireless power storage device ofthe invention.

FIG. 2 shows a structural example of a wireless power storage device ofthe invention.

FIGS. 3A and 3B show structural examples of charging and discharging ofa wireless power storage device of the invention.

FIGS. 4A and 4B show structural examples of a wireless power storagedevice of the invention.

FIGS. 5A and 5B show structural examples of a wireless power storagedevice of the invention.

FIG. 6 shows a structural example of a power feeder which supplieselectromagnetic waves to a wireless power storage device of theinvention.

FIGS. 7A and 7B show structural examples of a wireless power storagedevice of the invention.

FIGS. 8A and 8B show structural examples of a wireless power storagedevice of the invention.

FIG. 9 shows a structural example of a wireless power storage device ofthe invention.

FIG. 10 shows a structural example of a semiconductor device which isprovided with a wireless power storage device of the invention.

FIG. 11 shows a structural example of a semiconductor device which isprovided with a wireless power storage device of the invention.

FIG. 12 shows an example of an operation of a semiconductor device whichis provided with a wireless power storage device of the invention.

FIG. 13 shows a structural example of a wireless power storage device ofthe invention.

FIG. 14 shows a structural example of a reader/writer which supplieselectromagnetic waves to a semiconductor device which is provided with awireless power storage device of the invention.

FIGS. 15A to 15D show an example of a method of manufacturing a wirelesspower storage device of the invention.

FIGS. 16A to 16C show an example of a method of manufacturing a wirelesspower storage device of the invention.

FIGS. 17A and 17B show an example of a method of manufacturing awireless power storage device of the invention.

FIGS. 18A and 18B show an example of a method of manufacturing awireless power storage device of the invention.

FIGS. 19A and 19B show an example of a method of manufacturing awireless power storage device of the invention.

FIGS. 20A to 20E show examples of modes of usage of a wireless powerstorage device of the invention.

FIGS. 21A to 21D show examples of modes of usage of a wireless powerstorage device of the invention.

FIGS. 22A to 22D show examples of modes of usage of a wireless powerstorage device of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiment modes of the invention will be described withreference to the accompanying drawings. However, the invention can beimplemented in many different forms, and those skilled in the art willreadily appreciate that a variety of modifications can be made to themodes and their details without departing from the spirit and scope ofthe invention. Accordingly, the invention should not be construed asbeing limited to the description of the embodiment modes. Note that inthe structures of the invention which are described below, likereference numerals are used to indicate like parts throughout thedrawings.

Embodiment Mode 1

In this embodiment mode, an example of a wireless power storage deviceof the invention will be described with reference to the drawings.

A wireless power storage device 100 described in this embodiment modeincludes an antenna circuit 101, a rectifier circuit 102, a chargecontrol circuit 103, a battery 105, and a discharge control circuit 106(refer to FIG. 1). In the wireless power storage device 100, the battery105 is charged when an electromagnetic wave is received by the antennacircuit 101 and the received electromagnetic wave is input to thebattery 105 via the rectifier circuit 102. Further, the battery 105 isdischarged when electrical power charged to the battery 105 is suppliedto a load portion 107. The load portion 107 is provided with a circuitor the like which uses electrical power of the battery 105 to operate.Further, a structure in which the wireless power storage device 100 isprovided with the load portion 107 can also be employed. Note that astructure in which one or both of the charge control circuit 103 and thedischarge control circuit 106 are not provided may also be employed.

The antenna circuit 101 can include an antenna 451 and a resonantcapacitor 452. In this specification, the antenna 451 and the resonantcapacitor 452 are collectively referred to as the antenna circuit 101(refer to FIG. 4A).

The rectifier circuit 102 may be any circuit which converts analternating current signal, which is induced by an electromagnetic wavethat the antenna circuit 101 receives, into a direct current signal.Generally, the rectifier circuit 102 includes a diode and a smoothingcapacitor. It may also include a resistor or a capacitor in order toadjust impedance. For example, the rectifier circuit 102 may include adiode 453 and a smoothing capacitor 455, as shown in FIG. 4B.

The charge control circuit 103 may be any circuit which controls avoltage level of an electrical signal input from the rectifier circuit102 and outputs the electrical signal to the battery 105. For example,the charge control circuit 103 can include a regulator 401 which is acircuit that controls voltage, and a diode 403 which has rectifyingcharacteristics, as shown in FIG. 5A. The diode 403 prevents leakage ofelectrical power that is charged to the battery 105. Therefore, astructure in which the diode 403 is replaced with a switch 402 may beemployed, as shown in FIG. 5B. In a case where the switch 402 isprovided, by turning the switch on when the battery 105 is being chargedand off when the battery 105 is not being charged, leakage of electricalpower charged to the battery 105 can be prevented.

The electrical signal whose voltage level is controlled by the chargecontrol circuit 103 is input to the battery 105 and the battery 105 ischarged. Electrical power charged to the battery 105 is supplied to theload portion 107 through the discharge control circuit 106 (the battery105 is discharged).

The discharge control circuit 106 may be any circuit which controlsdischarging of the battery 105 by controlling a voltage level outputfrom the battery 105. For example, the discharge control circuit 106 caninclude a switch 501 and a regulator 502 which is a circuit thatcontrols voltage, as shown in FIG. 7A. By controlling on and off of theswitch 501, whether or not electrical power is supplied from the battery105 to the load portion 107 can be controlled.

Further, a structure in which on and off of the switch 501 arecontrolled in accordance with the voltage level of the battery 105 mayalso be employed. For example, the structure shown in FIG. 7A caninclude a Schmitt trigger 503 (refer to FIG. 7B). The Schmitt trigger503 can give hysteresis (a hysteresis characteristic) to a switchingelement. Specifically, with respect to input voltage, the structure hastwo threshold levels; an upper limit and a lower limit. On and off canbe controlled according to whether input is higher or lower than theselimits. For example, a structure in which the switch 501 is turned onwhen the voltage level of the battery 105 is equal to or greater than 5V and is turned off when the amount of voltage is equal to or less than3 V can be employed. In short, a structure in which electrical power issupplied to the load portion 107 only when a certain amount ofelectrical power is charged to the battery 105 can be employed.

Next, charging and discharging of the battery 105 provided in thewireless power storage device 100 described in this embodiment mode willbe described with reference to the drawings.

In the wireless power storage device described in this embodiment mode,the battery 105 is charged cumulatively, and the battery 105 isdischarged in pulses. Charging cumulatively refers to charging by takingin electromagnetic waves received by the antenna circuit 101 and addingthem together. The invention is not limited to the case whereelectromagnetic waves are taken in successively, and also includes thecase where they are taken in intermittently. Discharging is conducted inpulses refers to when the period of time the battery is discharged(electrical power is supplied to the load portion) for is shorter thanthe period of time the battery is charged for, and the battery isdischarged intermittently.

For example, the load portion 107 can be operated by charging thebattery 105 little by little, by taking in electromagnetic wavessuccessively over a certain period of time, and supplying the electricalpower which has been charged to the battery 105 to the load portion 107in a short period of time (refer to FIG. 3A).

Taking the wireless power storage device shown in FIG. 1 as an example,using electromagnetic waves taken in over a certain period of time,electrical power is stored in the battery 105 little by little, and whenthe potential of the battery 105 equals or exceeds a certain level, theswitch of the discharge control circuit 106 turns on and a large amountof electrical power is supplied to the load portion 107 in a pulse.Subsequently, electrical power can be supplied continuously to the loadportion 107 until the potential of the battery 105 falls below aspecified level. When the potential of the battery 105 falls below thespecified level, the switch of the discharge control circuit 106 turnsoff and supply of electrical power from the battery 105 to the loadportion 107 is stopped. Then, when the battery 105 is charged and thepotential of the battery 105 equals or exceeds the certain level, onceagain the switch of the discharge control circuit 106 turns on and alarge amount of electrical power is supplied to the load portion 107.

When electromagnetic waves are received over a certain period of timeand the battery 105 is charged, and the stored electrical power isdischarged in pulses, as described above, even when an electromagneticwave used for charging the battery 105 is weak, a large amount ofelectrical power can be supplied from the battery 105 to the loadportion. In this case, the period of time the battery 105 is charged foris longer than the period of time the battery 105 is discharged for.Further, the amount of electrical power discharged from the battery 105(the amount of electrical power supplied to the load portion 107) perunit time is larger than the amount of electrical power charged to thebattery 105 per unit time. Note that in FIG. 3A, an example is shown inwhich the antenna circuit 101 successively takes in electromagneticwaves and a given amount of electrical power is charged per unit time;however, the invention is not limited to the case where electromagneticwaves are taken in successively, and the battery 105 may be charged byintermittently taking in pulsed waves or modulated electromagneticwaves.

Note that in a case where electrical power charged to the battery 105 isdischarged to the load portion 107 in pulses, a structure may beemployed in which a switching circuit is provided between the dischargecontrol circuit 106 and the load portion 107, and the switching circuitturns on at periodic intervals, and thereby electrical power is suppliedto the load portion 107 intermittently. For example, a switching circuit133 can be provided between the discharge control circuit 106 and theload portion 107, and a clock generation circuit 131 and a frequencydivider circuit 132 can be used to control on and off of the switchprovided in the switching circuit 133 at periodic intervals (at aconstant frequency) (refer to FIG. 13). In such a case, electrical poweris supplied to the load portion 107 from the battery 105 when the switchprovided in the discharge control circuit 106 and the switch provided inthe switching circuit 133 are on. Further, a structure in whichelectrical power necessary for operations of the clock generationcircuit 131 and the frequency divider circuit 132 is supplied from thebattery 105 can be employed. Note that for the structure shown in FIG.13, control of the period of time of on and off of the switch providedin the switching circuit 133 and the like can be freely determined by apractitioner of the invention designing the clock generation circuit 131and the frequency divider circuit 132 as appropriate.

Further, in the case where electrical power charged to the battery 105is discharged to the load portion 107 in pulses, a structure can beemployed in which when the switch provided in the discharge controlcircuit 106 is in an on state, the load portion 107 operates at periodicintervals and receives electrical power from the battery 105.

In the wireless power storage device described in this embodiment mode,for the electromagnetic waves received by the antenna circuit 101,electromagnetic waves emitted from a power feeder which emitselectromagnetic waves at a specified wavelength may be used, andelectromagnetic waves generated at random outside may also be used. Thepower feeder may be any device which emits electromagnetic waves at aspecified wavelength, and preferably emits electromagnetic waves havinga wavelength such that they are easily received by the antenna providedin the antenna circuit. As electromagnetic waves which are generated atrandom outside, for example, electromagnetic waves from a mobiletelephone relay station (800 to 900 MHz band, 1.5 GHz, 1.9 to 2.1 GHzband, or the like), electromagnetic waves emitted from a mobiletelephone, electromagnetic waves from a wave clock (40 kHz or the like),noise from a household alternating current power supply (60 Hz or thelike), or the like can be used.

In the case of using a power feeder, a transmission method forelectromagnetic waves that is applied between the antenna circuit 101and the power feeder can be an electromagnetic coupling method, anelectromagnetic induction method, a microwave method, or the like. Thetransmission method may be selected as appropriate by a practitioner ofthe invention in consideration of an intended use. An antenna with alength and shape which are suitable for the transmission method may beprovided.

For example, in a case where an electromagnetic coupling method or anelectromagnetic induction method (e.g., 13.56 MHz band) is employed as atransmission method, since electromagnetic induction caused by changesin electric field density is used, a conductive film which serves as anantenna is formed with a circular shape (e.g., a loop antenna) or aspiral shape (e.g., a spiral antenna). Further, in the case of employinga microwave method (e.g., a UHF band (860 to 960 MHz band), a 2.45 GHzband, or the like) as a transmission method, the length and shape of aconductive film which serves as an antenna may be determined asappropriate taking a wavelength of an electromagnetic wave used forsignal transmission into consideration. For example, the conductive filmwhich serves as an antenna can be formed with a linear shape (e.g., adipole antenna), a flat shape (e.g., a patch antenna), or the like.Further, the shape of the conductive film which serves as an antenna isnot limited to a linear shape. Taking the wavelength of anelectromagnetic wave into consideration, the shape may be a curvedshape, a meandering shape, or a combination of these.

Note that a structure can be employed in which antenna circuits whicheach include antennas with different shapes are combined, so thatelectromagnetic waves with different frequency bands can be received. Asan example, shapes of antennas provided in antenna circuits in FIGS. 8Aand 8B will be described. For example, a structure may be employed inwhich an antenna 2902A and a 180 degrees omnidirectional (can receivesignals equally from any direction) antenna 2902B are disposed around achip 2901 which is provided with a battery, a load portion, and thelike, as shown in FIG. 8A. Alternatively, a structure may be employed inwhich an antenna 2902C with a thin coiled shape, an antenna 2902D forreceiving high-frequency electromagnetic waves, and an antenna 2902Ewhich extends in a long rod shape are disposed around a chip 2901 whichis provided with a battery, a load portion, and the like, as shown inFIG. 8B. When an antenna circuit which includes antennas which havedifferent shapes is provided, as shown in FIGS. 8A and 8B, a wirelesspower storage device which receives electromagnetic waves with differentfrequency bands (for example, electromagnetic waves from a power feederand electromagnetic waves generated at random outside) can be formed.

Further, in the case of using a power feeder, there is no particularlimitation on the frequency of electromagnetic waves transmitted fromthe power feeder to the antenna circuit 101, and for example, any of a300 GHz to 3 THz submillimeter wave, a 30 GHz to 300 GHz millimeterwave, a 3 GHz to 30 GHz microwave, a 300 MHz to 3 GHz ultrahighfrequency wave, a 30 MHz to 300 MHz very high frequency wave, a 3 MHz to30 MHz high frequency wave, a 300 kHz to 3 MHz medium frequency wave, a30 kHz to 300 kHz low frequency wave, and a 3 kHz to 30 kHz very lowfrequency wave can be used.

Further, ‘battery’ as referred to in this specification means a powerstorage means whose continuous operating time can be restored bycharging. Note that as power storage means, there are a secondary cell,a capacitor, and the like; however, in this specification, these powerstorage means are referred to under the general term ‘battery’. As abattery, although the type of battery used may differ depending on anintended use, preferably a battery formed with a sheet-like shape isused. For example, when a lithium battery is used, preferably a lithiumpolymer battery that uses a gel electrolyte, a lithium ion battery, orthe like, miniaturization is possible. Of course, any battery may beused as long as it is chargeable. A battery that can be charged and thatcan discharge, such as a nickel metal hydride battery, a nickel cadmiumbattery, an organic radical battery, a lead-acid battery, an airsecondary battery, a nickel-zinc battery, or a silver-zinc battery maybe used. A high-capacity capacitor or the like may also be used.

Note that as a capacitor which can be used as a battery in theinvention, it is desirable to use a capacitor having electrodes whoseopposing areas are large. In particular, it is preferable to use anelectric double layer capacitor which employs an electrode material witha large specific surface area such as activated carbon, fullerene, or acarbon nanotube. A capacitor has a simpler structure than a battery, caneasily be made thin, and can easily be formed by stacking layers. Anelectric double layer capacitor is preferable because it has a functionof storing electricity, does not deteriorate much even when the numberof times it is charged and discharged increases, and can be chargedquickly.

Note that in this embodiment mode, electrical power that is stored inthe battery is not limited to an electromagnetic wave received by theantenna circuit 101. A structure in which a power generation element issupplementarily provided in a part of the wireless power storage devicemay also be employed. Employing a structure in which a power generationelement is provided in the wireless power storage device is preferablebecause when such a structure is employed, the amount of electricalpower supplied for storage in the battery 105 can be increased and thecharging rate can be increased. As a power generation element, a powergeneration element which employs a solar cell, a power generationelement which employs a piezoelectric element, or a power generationelement which employs a micro electro mechanical system (a MEMS) may beused, for example.

When a battery which can be charged wirelessly is provided, as describedabove, a wireless power storage device can be charged easily. Further,when electromagnetic waves are received over a certain period of timeand thereby the battery is charged, and the stored electrical power isdischarged in pulses, a large amount of electrical power can be suppliedfrom the battery to a load portion even when an electromagnetic waveused for charging the battery is weak. In particular, the wireless powerstorage device described in this embodiment mode is very effective whenthe battery is charged by an antenna circuit receiving weakelectromagnetic waves which are generated at random outside.

Note that the wireless power storage device described in this embodimentmode can be combined with structures of wireless power storage devicesdescribed in other embodiment modes in this specification.

Embodiment Mode 2

In this embodiment mode, a structure which differs from the structure ofthe wireless power storage device described in the previous embodimentmode will be described with reference to the drawings.

The wireless power storage device 100 described in this embodiment modeincludes the antenna circuit 101, the rectifier circuit 102, the chargecontrol circuit 103, the battery 105, the discharge control circuit 106,a demodulation circuit 108, a modulation circuit 109, and acharge/discharge control circuit 110 (refer to FIG. 2). In the wirelesspower storage device 100, when an electromagnetic wave is received fromoutside by the antenna circuit 101 and the received electromagnetic waveis input to the battery 105 via the rectifier circuit 102, the battery105 is charged. Further, when electrical power charged to the battery105 is supplied to the load portion 107, the battery 105 is discharged.Note that the wireless power storage device described in this embodimentmode has the structure of the wireless power storage device 100described in the previous embodiment mode, with the addition of thedemodulation circuit 108, the modulation circuit 109, and thecharge/discharge control circuit 110.

The wireless power storage device 100 described in this embodiment modecan employ a structure where in the structure shown in FIG. 5B, thecharge control circuit 103 controls on and off of the switch 402 inaccordance with charging conditions of the battery 105. A structure inwhich on and off of the switch 402 are controlled by thecharge/discharge control circuit 110 can be employed.

The charge/discharge control circuit 110 may be any circuit whichmonitors charging conditions of the battery 105, and controls the switchprovided in the charge control circuit 103 and the switch provided inthe discharge control circuit 106 in accordance with charging conditionsof the battery 105. For example, a structure can be employed in whichthe charge/discharge control circuit 110 monitors the voltage level ofthe battery 105, and when the voltage level of the battery 105 equals orexceeds a certain level, the charge/discharge control circuit 110 turnsthe switch in the charge control circuit 103 off and turns the switch inthe discharge control circuit 106 on so that electrical power issupplied to the load portion 107. Further, a structure can be employedin which when the voltage level of the battery 105 falls below aspecified level, the charge/discharge control circuit 110 turns theswitch in the discharge control circuit 106 off and turns the switch inthe charge control circuit 103 on so that the battery 105 is charged.

By using the charge control circuit 103 to control charging of thebattery 105 in accordance with charging conditions of the battery 105 inthis manner, overcharging of the battery 105 when the battery 105 ischarged can be suppressed. Further, by turning the switch 402 of thecharge control circuit 103 off when the battery 105 is not beingcharged, leakage of electrical power charged to the battery 105 can beprevented.

Below, a case where the battery 105 is charged and discharged using apower feeder 201 will be described.

First, an electromagnetic wave input to the antenna circuit 101 from thepower feeder 201 is converted to an alternating current electricalsignal in the antenna circuit 101. The alternating current electricalsignal is rectified by the rectifier circuit 102, and then input to thecharge control circuit 103. Further, at the same time, a signal whichsignals the start of charging of the battery 105 is input to thecharge/discharge control circuit 110 via the demodulation circuit 108.When the signal which signals the start of charging is input, thecharge/discharge control circuit 110 controls on and off of the switchin the charge control circuit 103 in accordance with charging conditionsof the battery 105. For example, when the charge/discharge controlcircuit 110 monitors the voltage level of the battery 105 and thevoltage level of the battery 105 equals or falls below a certain level,the charge/discharge control circuit 110 turns on the switch provided inthe charge control circuit 103 and starts charging of the battery 105.

Note that in a case where it is not necessary to charge the battery 105when the voltage level of the battery 105 equals or exceeds a certainlevel, the switch in the charge control circuit 103 is turned off andthe battery 105 is not charged. In such a case, a signal which stopscharging of the battery 105 can be transmitted to the power feeder 201via the modulation circuit 109 and transmission of electromagnetic wavesfrom the power feeder 201 can be stopped.

Subsequently, the battery 105 is charged, and when the voltage of thebattery 105 equals or exceeds a certain level, the switch in the chargecontrol circuit 103 is turned off and charging of the battery 105 isterminated. Then, a signal which stops charging of the battery 105 canbe transmitted to the power feeder 201 via the modulation circuit 109and transmission of electromagnetic waves from the power feeder 201 canbe stopped.

Subsequently, the switch of the discharge control circuit 106 is turnedon, and electrical power is supplied from the battery 105 to the loadportion 107. The load portion 107 can use the electrical power suppliedfrom the battery 105 to operate a circuit provided in the load portion107. For example, a sensor can be provided in the load portion 107 andthe load portion 107 can use the electrical power supplied from thebattery 105 to intermittently operate the sensor. In such a case, asshown in FIG. 13 of Embodiment Mode 1, a switching circuit 133 may beprovided between the discharge control circuit 106 and the load portion107, and electrical power may be supplied from the battery 105 to thesensor intermittently.

Note that charging conditions of the battery 105 are monitored by thecharge/discharge control circuit 110, and when the voltage of thebattery 105 equals or falls below a certain level, the switch of thedischarge control circuit 106 is turned off, and discharging of thebattery 105 is stopped.

Further, in the wireless power storage device described in thisembodiment mode, the structure shown in FIG. 4A can be applied to theantenna circuit 101, and the structure shown in FIG. 4B can be appliedto the rectifier circuit 102. Further, the structure shown in FIG. 5B isapplied to the charge control circuit 103, and on and off of the switch402 is controlled by the charge/discharge control circuit 110. Further,a structure in which the discharge control circuit 106 has the structureshown in FIG. 7A and on and off of the switch 501 is controlled by thecharge/discharge control circuit 110 can be employed (refer to FIG. 9).

Further, the power feeder 201 in FIG. 2 can include a power transmissioncontrol portion 601 and an antenna circuit 602 (refer to FIG. 6). Thepower transmission control portion 601 modulates an electrical signal,which is for power transmission, that is transmitted to the wirelesspower storage device 100, and outputs an electromagnetic wave, which isfor power transmission, from the antenna circuit 602. In this embodimentmode, the antenna circuit 602 of the power feeder 201 shown in FIG. 6 isconnected to the power transmission control portion 601, and includes anantenna 603 and a resonant capacitor 604 which form an LC parallelresonant circuit. When power is transmitted, the power transmissioncontrol portion 601 supplies an induced current to the antenna circuit602, and outputs an electromagnetic wave, which is for powertransmission, to the wireless power storage device 100 from the antenna603.

Further, concerning the frequency of the signal transmitted from thepower feeder 201, any of a 300 GHz to 3 THz submillimeter wave, a 30 GHzto 300 GHz millimeter wave, a 3 GHz to 30 GHz microwave, a 300 MHz to 3GHz ultrahigh frequency wave, a 30 MHz to 300 MHz very high frequencywave, a 3 MHz to 30 MHz high frequency wave, a 300 kHz to 3 MHz mediumfrequency wave, a 30 kHz to 300 kHz low frequency wave, and a 3 kHz to30 kHz very low frequency wave can be used, for example.

Further, in the wireless power storage device 100 described in thisembodiment mode, charging of the battery is conducted cumulatively, anddischarging of the battery is conducted in pulses, as shown inEmbodiment Mode 1.

For example, a structure can be employed in which charging is stoppedwhen charging of the battery 105 is completed, and the battery 105 ischarged when the voltage level of the battery 105 equals or falls belowa certain level due to supply of electrical power to the load portion107 (refer to FIG. 3B). Concerning discharging of the battery 105, astructure may be employed in which the switch in the discharge controlcircuit 106 is kept on until the voltage level of the battery 105 equalsor falls below a certain level, and electrical power is supplied everytime the load portion 107 operates. A structure in which the switch ofthe discharge control circuit 106 is controlled using a signal fromoutside may also be employed.

When electromagnetic waves are received over a certain period of timeand the battery is charged, and the stored electrical power isdischarged in pulses, as described above, even when an electromagneticwave used for charging the battery is weak, a large amount of electricalpower can be supplied from the battery to the load portion. In thiscase, the period of time the battery is charged for is longer than theperiod of time the battery is discharged for. Further, the amount ofelectrical power discharged from the battery (the amount of electricalpower supplied to the load portion 107) per unit time is larger than theamount of electrical power charged to the battery per unit time.

When a battery which can be charged wirelessly is provided as describedabove, a wireless power storage device can be charged easily. Further,when electromagnetic waves are received over a certain period of timeand a battery is charged, and the stored electrical power is dischargedin pulses, even when an electromagnetic wave used for charging thebattery is weak, a large amount of electrical power can be supplied fromthe battery to a load portion.

Note that the wireless power storage device described in this embodimentmode can be combined with structures of wireless power storage devicesdescribed in other embodiment modes in this specification.

Embodiment Mode 3

In this embodiment mode, an example of a semiconductor device whichincludes a wireless power storage device described in either of theprevious embodiment modes (a semiconductor device provided with a signalprocessing circuit as a load) will be described with reference to thedrawings. Specifically, an RFID (radio frequency identification) tag(also referred to as an IC (integrated circuit) tag, an IC chip, an RFtag, a wireless tag, a wireless chip, and an electronic tag) will bedescribed as an example of a semiconductor device which communicatesdata via wireless communication. Note that the structure described inthis embodiment mode is not limited to an RFID tag, and can be appliedto any semiconductor device which communicates data via wirelesscommunication (e.g., an electronic device which includes a battery).

An example of a semiconductor device described in this embodiment modewill be described with reference to FIG. 10.

A semiconductor device 150 shown in FIG. 10 includes the antenna circuit101, a power supply portion 160, and a signal processing circuit 159.

The power supply portion 160 includes the rectifier circuit 102, thecharge control circuit 103, the battery 105, the discharge controlcircuit 106, the demodulation circuit 108, the modulation circuit 109,and the charge/discharge control circuit 110. Further, the signalprocessing circuit 159 includes an amplifier 152 (also referred to as anamplifier circuit), a demodulation circuit 151, a logic circuit 153, amemory control circuit 154, a memory circuit 155, a logic circuit 156,an amplifier 157, and a modulation circuit 158. Note that the structurein FIG. 10 differs from that in FIG. 2 of Embodiment Mode 2 in that thepower feeder 201 is replaced by a reader/writer 210 and the signalprocessing circuit 159 is connected to the discharge control circuit106.

Concerning the signal processing circuit 159, a communication signaltransmitted from the reader/writer 210 and received by the antennacircuit 101 is input to the demodulation circuit 151 and the amplifier152 in the signal processing circuit 159. Generally, the communicationsignal is a 13.56 MHz or 915 MHz signal or the like which undergoes ASKmodulation, PSK modulation, or the like, and is then transmitted. In acase where the communication signal is a 13.56 MHz signal, for example,it is desirable that the frequency of an electromagnetic wave forcharging the battery 105 which is transmitted from the reader/writer isthe same. Further, when a signal for charging and a signal forcommunication are in the same frequency band, the antenna circuit 101can be shared. When the antenna circuit 101 is shared, miniaturizationof the semiconductor device can be achieved.

In FIG. 10, in order to process a signal, a clock signal which serves asa reference is necessary. For example, a 13.56 MHz signal can be used asa clock signal. The amplifier 152 amplifies the 13.56 MHz signal andsupplies it to the logic circuit 153 as a clock signal. Further, acommunication signal which has been ASK modulated or PSK modulated isdemodulated by the demodulation circuit 151. The demodulated signal isalso transmitted to the logic circuit 153 and is analyzed. The signalwhich has been analyzed by the logic circuit 153 is transmitted to thememory control circuit 154. Based on that signal, the memory controlcircuit 154 controls the memory circuit 155, and data stored in thememory circuit 155 is extracted and transmitted to the logic circuit156. After being encoded by the logic circuit 156 the signal isamplified by the amplifier 157, and the modulation circuit 158 thenmodulates the amplified signal.

Note that a power supply for the signal processing circuit 159 in FIG.10 is supplied by the battery 105 through the discharge control circuit106. The semiconductor device 150 operates in this manner.

Further, an example of the reader/writer 210 in FIG. 10 will bedescribed with reference to FIG. 14. The reader/writer 210 includes areceiver portion 521, a transmitter portion 522, a controller portion523, an interface portion 524, and an antenna circuit 525. Thecontroller portion 523 controls data processing instructions and dataprocessing results of the receiver portion 521 and the transmitterportion 522 by control of a higher-order device 526 through theinterface portion 524. The transmitter portion 522 modulates a dataprocessing instruction which is transmitted to the semiconductor device150 and outputs it from the antenna circuit 525 as an electromagneticwave. Further, the receiver portion 521 demodulates a signal received bythe antenna circuit 525 and outputs it to the control portion 523 as adata processing result.

In this embodiment mode, the antenna circuit 525 of the reader/writer210 shown in FIG. 14 is connected to the receiver portion 521 and thetransmitter portion 522, and includes an antenna 527 and a resonantcapacitor 528 which form an LC parallel resonant circuit. Through asignal output by the semiconductor device 150, the antenna circuit 525receives electromotive force induced by the antenna circuit 525 as anelectrical signal. Further, an induced current is supplied to theantenna circuit 525, and a signal is transmitted from the antennacircuit 525 to the semiconductor device 150.

Next, an example of an operation in a case where the antenna circuit 101receives an electromagnetic wave from the reader/writer 210 will bedescribed with reference to FIG. 12. Note that here, an example isdescribed in which the charge control circuit 103 is provided with afirst switch and the discharge control circuit 106 is provided with asecond switch.

First, when an electromagnetic wave is transmitted from thereader/writer 210 (611), the antenna circuit 101 commences reception ofthe electromagnetic wave transmitted from the reader/writer 210 (612).Next, the charge/discharge control circuit 110 determines whether or notthe voltage of the battery 105 is equal to or greater than apredetermined voltage level (e.g., Vx) (613). Then, in the case wherethe voltage of the battery 105 is less than Vx, the second switchprovided in the discharge control circuit 106 is turned off so thatelectrical power of the battery 105 is not supplied to other circuits(614).

Next, the first switch is turned on (615) and charging of the battery105 commences (616). During charging, charging conditions of the battery105 are monitored by the charge/discharge control circuit 110, and thevoltage level of the battery 105 is monitored. Then, when the voltage ofthe battery 105 equals or exceeds the predetermined voltage level, thefirst switch provided in the charge control circuit 103 is turned off(617), and charging is terminated (618).

Next, the second switch is turned on at the same time as or after thefirst switch is turned off (619); electrical power is supplied to acircuit provided in the signal processing circuit 159 through thedischarge control circuit 106; and the semiconductor device 150transmits an electromagnetic wave which contains a signal for startingcommunication (hereinafter also referred to as simply a ‘signal’) to thereader/writer 210 (620). Then, after the reader/writer 210 has receivedthe signal (621), necessary information is transmitted to thesemiconductor device 150 (622). The semiconductor device 150 receivesthe signal transmitted from the reader/writer 210 (623), processes thereceived signal (624), and transmits a reply signal (625). Then, thereader/writer 210 receives the signal transmitted from the semiconductordevice 150 (626), and then terminates communication (627).

Note that in the structure shown in FIG. 10, a case where the powersupply portion 160 and the signal processing circuit 159 share theantenna circuit 101 is shown; however, a structure in which the powersupply portion 160 and the signal processing circuit 159 each have anantenna circuit may be employed. A structure in which the power supplyportion 160 is provided with a first antenna circuit 161 and the signalprocessing circuit 159 is provided with a second antenna circuit 162 isdescribed with reference to FIG. 11. Note that FIG. 11 illustrates acase where the first antenna circuit 161 receives electromagnetic waveswhich are generated at random outside, and the second antenna circuit162 receives electromagnetic waves having a specified wavelength whichare transmitted from the reader/writer 210. That is, a structure inwhich the first antenna circuit 161 receives an electromagnetic wavehaving a different frequency to that of an electromagnetic wave whichthe second antenna circuit 162 receives can be employed.

In the semiconductor device shown in FIG. 11, the first antenna circuit161 takes in a weak electromagnetic wave generated at random outside,and the battery 105 is charged little by little over a certain amount oftime. Note that the charge/discharge control circuit 110 monitorscharging conditions of the battery 105, and prevents overcharging of thebattery 105 by controlling on and off of the switches provided in thecharge control circuit 103 and the discharge control circuit 106.Further, here, a structure is shown in which electrical power charged tothe battery 105 is supplied to a sensor portion 190 provided in thesemiconductor device 150.

Further, the second antenna circuit 162 receives an electromagnetic wavehaving a specified wavelength which is transmitted from thereader/writer 210, and information is transmitted and received betweenthe semiconductor device 150 and the reader/writer 210. By providing arectifier circuit 163 and a power supply circuit 164 in the signalprocessing circuit 159, electrical power necessary for transmission andreception of information between the semiconductor device 150 and thereader/writer 210 can be secured. Note that a structure may be employedwhere in the signal processing circuit 159, electrical power is suppliedfrom the battery 105 when more electrical power is necessary.

Further, supply of electrical power to the sensor 190 can be performedby controlling the switch provided in the discharge control circuit 106through the charge/discharge control circuit 110 based on a signalreceived from outside by the signal processing circuit 159 (a signalwhich operates the sensor portion 190).

Further, as shown in FIG. 13 of Embodiment Mode 1, a structure may beemployed in which a switching circuit 133 is provided between thedischarge control circuit 106 and the sensor portion 190, and the sensorportion 190 is operated by intermittently supplying electrical powerfrom the battery 105 to the sensor portion 190. In that case, astructure can be employed in which information from when the sensorportion 190 periodically operates is stored in the memory circuit of thesignal processing circuit 159, and when transmission and reception ofinformation between the reader/writer 210 and the semiconductor device150 are performed, the information stored in the memory circuit istransmitted to the reader/writer 210.

As described above, by providing a battery capable of wireless charging,a wireless power storage device provided in a semiconductor device caneasily be charged. Further, when electromagnetic waves are received overa certain period of time and the battery is charged cumulatively, andthe stored electrical power is discharged in pulses, a large amount ofelectrical power can be supplied from the battery to a load portion evenwhen an electromagnetic wave used for charging the battery is weak. Inparticular, the semiconductor device described in this embodiment modeis effective when the battery is charged by the antenna circuitreceiving weak electromagnetic waves generated at random outside.

Note that the semiconductor device structure described in thisembodiment mode can be combined with structures of wireless powerstorage devices described in other embodiment modes in thisspecification.

Embodiment Mode 4

In this embodiment mode, an example of a manufacturing method of thesemiconductor device described in Embodiment Mode 3 will be describedwith reference to the drawings. In this embodiment mode, a structure inwhich an antenna circuit, a power supply portion, and a signalprocessing circuit are provided over the same substrate will bedescribed. Note that it is desirable to form the antenna circuit, thepower supply portion, and the signal processing circuit over substrateat one time and to employ thin film transistors (TFTs) as transistorsincluded in the power supply portion and the signal processing circuit,because thereby miniaturization can be achieved.

First, as shown in FIG. 15A, a separation layer 1903 is formed over asurface of a substrate 1901 with an insulating film 1902 therebetween.Next, an insulating film 1904 which serves as a base film and asemiconductor film 1905 (e.g., a film which includes amorphous silicon)are stacked. Note that the insulating film 1902, the separation layer1903, the insulating film 1904, and the semiconductor film 1905 can beformed in succession.

Further, the substrate 1901 may be a glass substrate, a quartzsubstrate, a metal substrate (e.g. a stainless steel substrate or thelike), a ceramic substrate, or a semiconductor substrate, such as a Sisubstrate. Alternatively, a plastic substrate formed of polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone(PES), acrylic, or the like can be used. Note that in this step, theseparation layer 1903 is provided over an entire surface of thesubstrate 1901 with the insulating film 1902 interposed therebetween;however, if necessary, the separation layer may be selectively providedby using a photolithography method after providing the separation layerover an entire surface of the substrate 1901.

The insulating film 1902 and the insulating film 1904 are formed usingan insulating material such as silicon oxide, silicon nitride, siliconoxynitride (SiOxNy, where x>y), or silicon nitride oxide (SiNxOy, wherex>y), by a CVD method, a sputtering method, or the like. For example,when the insulating film 1902 and the insulating film 1904 have atwo-layer structure, preferably a silicon nitride oxide film is formedas a first insulating film and a silicon oxynitride film is formed as asecond insulating film. Alternatively, a silicon nitride film may beformed as a first insulating film and a silicon oxide film may be formedas a second insulating film. The insulating film 1902 serves as ablocking layer which prevents an impurity element from the substrate1901 from being mixed into the separation layer 1903 or an elementformed thereover. The insulating film 1904 serves as a blocking layerwhich prevents an impurity element from the substrate 1901 or theseparation layer 1903 from being mixed into an element formed thereover.By forming the insulating films 1902 and 1904 which serve as blockinglayers in this manner, an element formed thereover can be prevented frombeing adversely affected by an alkali metal such as Na or an alkaliearth metal from the substrate 1901, or an impurity element included inthe separation layer 1903. Note that when quartz is used as thesubstrate 1901, the insulating films 1902 and 1904 may be omitted fromthe structure.

As the separation layer 1903, a metal film, a stacked-layer structureincluding a metal film and a metal oxide film, or the like can be used.As the metal film, a single-layer structure or a stacked-layer structureis formed using a film formed of any of the elements tungsten (W),molybdenum (Mo), titanium (Ti), tantalum (Ta), niobium (Nb), nickel(Ni), cobalt (Co), zirconium (Zr), zinc (Zn), ruthenium (Ru), rhodium(Rh), palladium (Pd), osmium (Os), and iridium (Ti), or of an alloymaterial or a compound material containing such an element as a mainconstituent. These materials can be formed by using a sputtering method,various CVD methods, such as a plasma CVD method, or the like. As thestacked-layer structure including a metal film and a metal oxide film,after the aforementioned metal film is formed, plasma treatment in anoxygen atmosphere or an N₂O atmosphere, or heat treatment in an oxygenatmosphere or an N₂O atmosphere is performed, so that an oxide or anoxynitride of the metal film can be formed on a surface of the metalfilm. For example, when a tungsten film is formed as the metal film by asputtering method, a CVD method, or the like, plasma treatment isperformed on the tungsten film so that a metal oxide film formed oftungsten oxide can be formed on a surface of the tungsten film.

The semiconductor film 1905 is formed with a thickness of 25 to 200 nm(preferably, 30 to 150 nm) by a sputtering method, an LPCVD method, aplasma CVD method, or the like.

Next, as shown in FIG. 15B, the semiconductor film 1905 is crystallizedby being irradiated with laser light. The semiconductor film 1905 may becrystallized by a method which combines laser light irradiation with athermal crystallization method which employs RTA or an annealing furnaceor a thermal crystallization method which employs a metal element forpromoting crystallization, or the like. Subsequently, the obtainedcrystalline semiconductor film is etched into a desired shape to formcrystallized crystalline semiconductor films 1905 a to 1905 f, and agate insulating film 1906 is formed so as to cover the semiconductorfilms 1905 a to 1905 f.

Note that the gate insulating film 1906 is formed using an insulatingmaterial such as silicon oxide, silicon nitride, silicon oxynitride, orsilicon nitride oxide, by a CVD method, a sputtering method, or thelike. For example, when the gate insulating film 1906 has a two-layerstructure, preferably a silicon oxynitride film is formed as a firstinsulating film and a silicon nitride oxide film is formed as a secondinsulating film. Alternatively, a silicon oxide film may be formed asthe first insulating film and a silicon nitride film may be formed asthe second insulating film.

An example of a manufacturing step of the crystalline semiconductorfilms 1905 a to 1905 f is briefly described below. First, an amorphoussemiconductor film with a film thickness of 50 to 60 nm is formed by aplasma CVD method. Next, a solution containing nickel, which is a metalelement for promoting crystallization, is retained on the amorphoussemiconductor film, and then dehydrogenation treatment (at 500° C., forone hour) and thermal crystallization treatment (at 550° C., for fourhours) are performed on the amorphous semiconductor film to form acrystalline semiconductor film. Subsequently, the crystallinesemiconductor film is irradiated with laser light, and the crystallinesemiconductor films 1905 a to 1905 f are formed by using aphotolithography method. Note that the amorphous semiconductor film maybe crystallized just by laser light irradiation, without performingthermal crystallization which employs a metal element for promotingcrystallization.

Note that as a laser oscillator for crystallization, a continuous wavelaser beam (a CW laser beam) or a pulsed wave laser beam (a pulsed laserbeam) can be used. As a laser beam which can be used here, a laser beamemitted from one or more of the following can be used: a gas laser, suchas an Ar laser, a Kr laser, or an excimer laser; a laser whose medium issingle crystalline YAG, YVO₄, forsterite (Mg₂SiO₄), YAlO₃, or GdVO₄, towhich one or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta has been addedas a dopant; or polycrystalline (ceramic) YAG; Y₂O₃, YVO₄, YAlO₃, orGdVO₄, to which one or more of Nd, Yb, Cr, Ti, Ho, Er, Tm, and Ta hasbeen added as a dopant; a glass laser; a ruby laser; an alexandritelaser; a Ti:sapphire laser; a copper vapor laser; or a gold vapor laser.Crystals with a large grain size can be obtained by irradiation withfundamental waves of such laser beams or second to fourth harmonics ofthe fundamental waves. For example, the second harmonic (532 nm) or thethird harmonic (355 nm) of an Nd:YVO₄ laser (fundamental wave of 1064nm) can be used. In this case, a power density of approximately 0.01 to100 MW/cm² (preferably, 0.1 to 10 MW/cm²) is necessary. Irradiation isconducted with a scanning rate of approximately 10 to 2000 cm/sec. Notethat a laser using, as a medium, single crystalline YAG YVO₄, forsterite(Mg₂SiO₄), YAlO₃, or GdVO₄, to which one or more of Nd, Yb, Cr, Ti, Ho,Er, Tm, and Ta has been added as a dopant, or polycrystalline (ceramic)YAG, Y₂O₃, YVO₄, YAlO₃, or GdVO₄, to which one or more of Nd, Yb, Cr,Ti, Ho, Er, Tm, and Ta has been added as a dopant; an Ar ion laser; or aTi:sapphire laser, can be continuously oscillated. Furthermore, pulseoscillation thereof can be performed at a repetition rate of 10 MHz ormore by performing Q-switch operation, mode locking, or the like. When alaser beam is oscillated at a repetition rate of 10 MHz or more, duringthe time in which a semiconductor film is melted by the laser beam andthen solidifies, the semiconductor film is irradiated with a next pulse.Accordingly, unlike in a case of using a pulsed laser with a lowrepetition rate, a solid-liquid interface can be continuously moved inthe semiconductor film; therefore, crystal grains which have growncontinuously in a scanning direction can be obtained.

Further, high-density plasma treatment may be performed on thesemiconductor films 1905 a to 1905 f to oxidize or nitride surfacesthereof, to form the gate insulating film 1906. For example, the gateinsulating film 1906 is formed by plasma treatment in which a mixed gaswhich contains a rare gas such as He, Ar, Kr, or Xe, and oxygen,nitrogen oxide (NO₂), ammonia, nitrogen, hydrogen, or the like, isintroduced. When excitation of the plasma in this case is performed byintroduction of a microwave, high density plasma can be generated at alow electron temperature. The surface of the semiconductor film can beoxidized or nitrided by oxygen radicals (OH radicals may be included) ornitrogen radicals (NH radicals may be included) generated by thishigh-density plasma.

By treatment using such high-density plasma, an insulating film with athickness of 1 to 20 nm, typically 5 to 10 nm, is formed over thesemiconductor film. Because the reaction in this case is a solid-phasereaction, interface state density between the insulating film and thesemiconductor film can be made very low. Because such high-densityplasma treatment oxidizes (or nitrides) a semiconductor film(crystalline silicon, or polycrystalline silicon) directly, theinsulating film can be formed with very little unevenness in itsthickness. In addition, since crystal grain boundaries of crystallinesilicon are also not strongly oxidized, very favorable conditionsresult. That is, by the solid-phase oxidation of the surface of thesemiconductor film by the high-density plasma treatment shown here, aninsulating film with good uniformity and low interface state density canbe formed without excessive oxidation at crystal grain boundaries.

Note that as the gate insulating film 1906, just an insulating filmformed by the high-density plasma treatment may be used, or aninsulating film of silicon oxide, silicon oxynitride, silicon nitride,or the like may be formed thereover by a CVD method which employs plasmaor a thermal reaction, to make stacked layers. In any case, whentransistors include an insulating film formed by high-density plasma ina part of a gate insulating film or in the whole of a gate insulatingfilm, unevenness in characteristics can be reduced.

Furthermore, in the semiconductor films 1905 a to 1905 f which areobtained by crystallizing a semiconductor film by irradiation with acontinuous wave laser beam or a laser beam oscillated at a repetitionrate of 10 MHz or more which is scanned in one direction, crystals growin the scanning direction of the beam. When transistors are disposed sothat the scanning direction is aligned with the channel length direction(the direction in which a carrier flows when a channel formation regionis formed) and the above-described gate insulating layer is used incombination with the transistors, thin film transistors with lessvariation in characteristics and high electron field-effect mobility canbe obtained.

Next, a first conductive film and a second conductive film are stackedover the gate insulating film 1906. In this embodiment mode, the firstconductive film is formed with a thickness of 20 to 100 nm using a CVDmethod, a sputtering method, or the like. The second conductive film isformed with a thickness of 100 to 400 nm. The first conductive film andthe second conductive film are formed using an element such as tantalum(Ta), tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (AI),copper (Cu), chromium (Cr), or niobium (Nb), or using an alloy materialor a compound material containing such an element as its mainconstituent. Alternatively, they are formed using a semiconductormaterial typified by polycrystalline silicon doped with an impurityelement such as phosphorus. As examples of a combination of the firstconductive film and the second conductive film, a tantalum nitride filmand a tungsten film, a tungsten nitride film and a tungsten film, amolybdenum nitride film and a molybdenum film, and the like can begiven. Because tungsten and tantalum nitride have high heat resistance,heat treatment for thermal activation can be performed after the firstconductive film and the second conductive film are formed. In addition,in the case of using a three-layer structure instead of a two-layerstructure, a stacked-layer structure including a molybdenum film, analuminum film, and a molybdenum film may be used.

Next, a resist mask is formed using a photolithography method, andetching treatment for forming a gate electrode and a gate line isconducted, forming gate electrodes 1907 over the semiconductor films1905 a to 1905 f. In this embodiment mode, an example in which the gateelectrodes 1907 have a stacked-layer structure which includes a firstconductive film 1907 a and a second conductive film 1907 b is described.

Next, as shown in FIG. 15C, the gate electrodes 1907 are used as masks,and an impurity element imparting n-type conductivity is added to thesemiconductor films 1905 a to 1905 f at a low concentration by an iondoping method or an ion implantation method. Subsequently, a resist maskis selectively formed by a photolithography method, and an impurityelement imparting p-type conductivity is added at a high concentrationto the semiconductor films 1905 a to 1905 f. As an impurity elementwhich exhibits n-type conductivity, phosphorus (P), arsenic (As), or thelike can be used. As an impurity element which exhibits p-typeconductivity, boron (B), aluminum (Al), gallium (Ga), or the like can beused. Here, phosphorus (P) is used as an impurity element which impartsn-type conductivity, and is selectively introduced into thesemiconductor films 1905 a to 1905 f such that they contain phosphorus(P) at a concentration of 1×10¹⁵ to 1×10¹⁹/cm³. Thus, n-type impurityregions 1908 are formed. Further, boron (B) is used as an impurityelement which imparts p-type conductivity, and is selectively introducedinto the semiconductor films 1905 c and 1905 e such that they containboron (B) at a concentration of 1×10¹⁹ to 1×10²⁰/cm³. Thus, p-typeimpurity regions 1909 are formed.

Next, an insulating film is formed so as to cover the gate insulatingfilm 1906 and the gate electrodes 1907. The insulating film is formed asa single layer or stacked layers of a film containing an inorganicmaterial such as silicon, an oxide of silicon, or a nitride of silicon,or a film containing an organic material such as an organic resin, by aplasma CVD method, a sputtering method, or the like. Next, theinsulating film is selectively etched using anisotropic etching whichetches mainly in a vertical direction, forming insulating films 1910(also referred to as side walls) which are in contact with side surfacesof the gate electrodes 1907. The insulating films 1910 are used as masksfor doping when LDD (lightly doped drain) regions are formed.

Next, using a resist mask formed by a photolithography method, the gateelectrodes 1907, and the insulating films 1910 as masks, an impurityelement which imparts n-type conductivity is added at a highconcentration to the semiconductor films 1905 a, 1905 b, 1905 d, and1905 f, to form n-type impurity regions 1911. Here, phosphorus (P) isused as an impurity element which imparts n-type conductivity, and it isselectively introduced into the semiconductor films 1905 a, 1905 b, 1905d, and 1905 f such that they contain phosphorus (P) at a concentrationof 1×10¹⁹ to 1×10²⁰/cm³. Thus the n-type impurity regions 1911, whichhave a higher concentration than the impurity regions 1908, are formed.

By the above-described steps, N-channel thin film transistors 1900 a,1900 b, 1900 d, and 1900 f, and p-channel thin film transistors 1900 cand 1900 e are formed, as shown in FIG. 15D.

Note that in the n-channel thin film transistor 1900 a, a channelformation region is formed in a region of the semiconductor film 1905 awhich overlaps with the gate electrode 1907; the impurity regions 1911which each form either a source region or a drain region are formed inregions which do not overlap with the gate electrode 1907 and theinsulating films 1910; and lightly doped drain regions (LDD regions) areformed in regions which overlap with the insulating films 1910 and whichare between the channel formation region and the impurity regions 1911.Further, the n-channel thin film transistors 1900 b, 1900 d, and 1900 fare similarly provided with channel formation regions, lightly dopeddrain regions, and impurity regions 1911.

Further, in the p-channel thin film transistor 1900 c, a channelformation region is formed in a region of the semiconductor film 1905 cwhich overlaps with the gate electrode 1907, and the impurity regions1909 which each form either a source region or a drain region are formedin regions which do not overlap with the gate electrode 1907. Further,the p-channel thin film transistor 1900 e is similarly provided with achannel formation region and impurity regions 1909. Note that here, thep-channel thin film transistors 1900 c and 1900 e are not provided withLDD regions; however, the p-channel thin film transistors may beprovided with an LDD region, and the n-channel thin film transistor isnot necessarily provided with an LDD region.

Next, as shown in FIG. 16A, an insulating film is formed as a singlelayer or stacked layers so as to cover the semiconductor films 1905 a to1905 f, the gate electrodes 1907, and the like; and conductive films1913, which are electrically connected to the impurity regions 1909 and1911 which form the source regions or the drain regions of the thin filmtransistors 1900 a to 1900 f, are formed over the insulating film Theinsulating film is formed as a single layer or stacked layers, using aninorganic material, such as an oxide of silicon or a nitride of silicon,an organic material, such as a polyimide, a polyamide, benzocyclobutene,an acrylic, or an epoxy, a siloxane material, or the like, by a CVDmethod, a sputtering method, an SOG method, a droplet discharge method,a screen printing method, or the like. Here, the insulating film has atwo-layer structure. A silicon nitride oxide film is formed as a firstinsulating film 1912 a, and a silicon oxynitride film is formed as asecond insulating film 1912 b. Further, the conductive films 1913 formsource electrodes and drain electrodes of the thin film transistors 1900a to 1900 f.

Note that before the insulating films 1912 a and 1912 b are formed orafter one or more thin films of the insulating films 1912 a and 1912 bare formed, heat treatment is preferably conducted for recovering thecrystallinity of the semiconductor film, for activating an impurityelement which has been added to the semiconductor film, or forhydrogenating the semiconductor film. As the heat treatment, thermalannealing, a laser annealing method, an RTA method, or the like ispreferably used.

The conductive films 1913 are formed as a single layer or stackedlayers, using any of the elements aluminum (AI), tungsten (W), titanium(Ti), tantalum (Ta), molybdenum (Mo), nickel (Ni), platinum (Pt), copper(Cu), gold (Au), silver (Ag), manganese (Mn), neodymium (Nd), carbon(C), and silicon (Si), or an alloy material or a compound materialcontaining one of the above-mentioned elements as its main constituent,by a CVD method, a sputtering method, or the like. An alloy materialcontaining aluminum as its main constituent corresponds to, for example,a material which contains aluminum as its main constituent and alsocontains nickel, or an alloy material which contains aluminum as itsmain constituent and which also contains nickel and one or both ofcarbon and silicon. The conductive films 1913 preferably employ, forexample, a stacked-layer structure including a barrier film, analuminum-silicon (Al—Si) film, and a barrier film, or a stacked-layerstructure including a barrier film, an aluminum-silicon (Al—Si) film, atitanium nitride film, and a barrier film. Note that a barrier filmcorresponds to a thin film formed from titanium, a nitride of titanium,molybdenum, or a nitride of molybdenum. Aluminum and aluminum silicon,which have low resistance and are inexpensive, are ideal materials forforming the conductive films 1913. Further, generation of a hillock ofaluminum or aluminum silicon can be prevented when upper and lowerbarrier layers are formed. Furthermore, when the barrier film is formedfrom titanium, which is a highly-reducible element, even if a thinnatural oxide film is formed over the crystalline semiconductor film,the natural oxide film is chemically reduced, so good contact with thecrystalline semiconductor film can be obtained.

Next, an insulating film 1914 is formed so as to cover the conductivefilms 1913, and over the insulating film 1914, conductive films 1915 aand 1915 b, which are each electrically connected to the conductivefilms 1913 which form source electrodes and drain electrodes of the thinfilm transistors 1900 a and 1900 f, are formed. Further, conductivefilms 1916 a and 1916 b, which are each electrically connected to theconductive films 1913 which form source electrodes and drain electrodesof the thin film transistors 1900 b and 1900 e, are formed. Note thatthe conductive films 1915 a and 1915 b may be formed of the samematerial at the same time as the conductive films 1916 a and 1916 b. Theconductive films 1915 a and 1915 b and the conductive films 1916 a and1916 b can be formed using any of the materials that the conductivefilms 1913 can be formed of, mentioned above.

Next, as shown in FIG. 16B, conductive films 1917 a and 1917 b whichserve as antennas are formed such that they are electrically connectedto the conductive films 1916 a and 1916 b. Here, one of the conductivefilms 1917 a and 1917 b which serve as antennas corresponds to anantenna of the first antenna circuit described in a previous embodimentmode, and the other one of the conductive films 1917 a and 1917 b whichserve as antennas corresponds to an antenna of the second antennacircuit. For example, if the conductive film 1917 a is the antenna ofthe first antenna circuit and the conductive film 1917 b is the antennaof the second antenna circuit, the thin film transistors 1900 a to 1900c serve as the first signal processing circuit which is described in aprevious embodiment mode, and the thin film transistors 1900 d to 1900 fserve as the second signal processing circuit described in a previousembodiment mode.

Note that the insulating film 1914 can be provided by a CVD method, asputtering method, or the like as a single-layer structure whichincludes an insulating film containing oxygen and/or nitrogen, such assilicon oxide, silicon nitride, silicon oxynitride, or silicon nitrideoxide; or a film containing carbon, such as DLC (diamond-like carbon);or an organic material, such as epoxy, polyimide, polyamide, polyvinylphenol, benzocyclobutene, or acrylic; or a siloxane material, such as asiloxane resin. Alternatively, the insulating film 1914 may have astacked structure including the above-mentioned materials. Note that asiloxane material corresponds to a material having a Si—O—Si bond.Siloxane has a backbone structure formed of bonds of silicon (Si) andoxygen (O). As a substituent, an organic group containing at leasthydrogen (for example, an alkyl group or aromatic hydrocarbon) is used.A fluoro group can also be used as a substituent. Alternatively, anorganic group containing at least hydrogen and a fluoro group may beused as a substituent.

The conductive films 1917 a and 1917 b are formed from a conductivematerial, using a CVD method, a sputtering method, a printing method,such as a screen printing method or a gravure printing method, a dropletdischarge method, a dispensing method, a plating method, or the like.The conductive material is any of the elements aluminum (Al), titanium(Ti), silver (Ag), copper (Cu), gold (Au), platinum (Pt), nickel (Ni),palladium (Pd), tantalum (Ta), and molybdenum (Mo), or an alloy materialor a compound material containing one of the above-mentioned elements asits main constituent, and has a single-layer structure or astacked-layer structure.

For example, in the case of using a screen printing method to form theconductive films 1917 a and 1917 b which serve as antennas, theconductive films 1917 a and 1917 b can be provided by selectivelyprinting a conductive paste in which conductive particles having a grainsize of several nm to several tens of μm are dissolved or dispersed inan organic resin. As conductive particles, metal particles of one ormore of any of silver (Ag), gold (Au), copper (Cu), nickel (Ni),platinum (Pt), palladium (Pd), tantalum (Ta), molybdenum (Mo), titanium(Ti), and the like; fine particles of silver halide; or dispersivenanoparticles can be used. In addition, as the organic resin included inthe conductive paste, one or more organic resins selected from amongorganic resins which serve as a binder, a solvent, a dispersing agent,or a coating material for the metal particles can be used. An organicresin such as an epoxy resin or a silicon resin can be given asrepresentative examples. Further, when the conductive film is formed, itis preferable to conduct baking after the conductive paste is applied.For example, in the case of using fine particles containing silver as amain constituent (e.g., the grain size is in the range of 1 nm to 100nm, inclusive) as a material for the conductive paste, the conductivefilm can be obtained by curing by baking at a temperature in the rangeof 150 to 300° C. Alternatively, fine particles containing solder orlead-free solder as a main constituent may be used. In that case,preferably fine particles having a grain size of 20 μm or less are used.Solder and lead-free solder have advantages such as low cost.

Further, the conductive films 1915 a and 1915 b can each serve as awiring which is electrically connected to a battery in a subsequentprocess. Furthermore, when the conductive films 1917 a and 1917 b whichserve as antennas are formed, another conductive film may be separatelyformed such that it is electrically connected to the conductive films1915 a and 1915 b, and that conductive film may be used as a wiringconnected to the battery. Note that the conductive films 1917 a and 1917b in FIG. 16B correspond to the first antenna circuit and the secondantenna circuit described in Embodiment Mode 1.

Next, as shown in FIG. 16C, an insulating film 1918 is formed so as tocover the conductive films 1917 a and 1917 b, and then a layer(hereinafter referred to as an element formation layer 1919) includingthe thin film transistors 1900 a to 1900 f, the conductive films 1917 aand 1917 b, and the like, is separated from the substrate 1901. Here,after using laser light (e.g., UV light) irradiation to form openings inregions where the thin film transistors 1900 a to 1900 f are not formed,the element formation layer 1919 can be separated from the substrate1901 using physical force. Alternatively, before the element formationlayer 1919 is separated from the substrate 1901, an etchant may beintroduced into the formed openings to selectively remove the separationlayer 1903. As the etchant, a gas or liquid containing halogen fluorideor an interhalogen compound is used. For example, chlorine trifluoride(ClF₃) is used as a gas containing halogen fluoride. Accordingly, theelement formation layer 1919 is separated from the substrate 1901. Notethat the separation layer 1903 may be partially left instead of beingremoved entirely. By leaving a part of the separation layer 1903,consumption of the etchant and treatment time required for removing theseparation layer can be reduced. Further, the element formation layer1919 can be left over the substrate 1901 after the separation layer 1903is removed. Furthermore, by reusing the substrate 1901 after the elementformation layer 1919 is separated from it, cost can be reduced.

The insulating film 1918 can be formed using a CVD method, a sputteringmethod, or the like as a single-layer structure including an insulatingfilm which contains oxygen and/or nitrogen, such as silicon oxide,silicon nitride, silicon oxynitride, or silicon nitride oxide; or a filmcontaining carbon, such as DLC (diamond-like carbon); or an organicmaterial such as epoxy, polyimide, polyamide, polyvinyl phenol,benzocyclobutene, or acrylic; or a siloxane material such as a siloxaneresin. Alternatively, the insulating film 1918 can have a stacked-layerstructure including one or more of the above-mentioned films.

In this embodiment mode, as shown in FIG. 17A, the openings are formedin the element formation layer 1919 by laser light irradiation, and thena first sheet material 1920 is attached to one surface of the elementformation layer 1919 (a surface where the insulating film 1918 isexposed). Then, the element formation layer 1919 is separated from thesubstrate 1901.

Next, as shown in FIG. 17B, a second sheet material 1921 is attached tothe other surface of the element formation layer 1919 (a surface exposedby separation) by performing one or both of heat treatment and pressuretreatment. As the first sheet material 1920 and the second sheetmaterial 1921, a hot-melt film or the like can be used.

As the first sheet material 1920 and the second sheet material 1921,films on which antistatic treatment for preventing static electricity orthe like has been performed (hereinafter referred to as antistaticfilms) can be used. Examples of antistatic films are films in which amaterial that can prevent electrostatic charge is dispersed in a resin,films to which a material that can prevent electrostatic charge isattached, and the like. A film provided with a material that can preventelectrostatic charge may be a film which has a material that can preventelectrostatic charge provided over one of its surfaces, or a film whichhas a material that can prevent electrostatic charge provided over bothof its surfaces. Concerning the film which has a material that canprevent electrostatic charge provided over one of its surfaces, the filmmay be attached to the layer such that the material that can preventelectrostatic charge is on the inner side of the film or the outer sideof the film. Note that the material that can prevent electrostaticcharge may be provided over an entire surface of the film, or over apart of the film. As a material that can prevent electrostatic charge, ametal, indium tin oxide (ITO), or a surfactant such as an amphotericsurfactant, a cationic surfactant, or a nonionic surfactant can be used.In addition to that, as an antistatic material, a resin materialcontaining a cross-linked copolymer having a carboxyl group and aquaternary ammonium base on its side chain, or the like can be used. Byattaching, mixing, or applying such a material to a film, an antistaticfilm can be formed. By performing sealing using the antistatic film, theextent to which a semiconductor element is affected by staticelectricity from outside and the like when dealt with as a product canbe reduced.

Note that the battery is formed such that it is connected to theconductive films 1915 a and 1915 b. The connection with the battery maybe made before the element formation layer 1919 is separated from thesubstrate 1901 (at a stage shown in FIG. 16B or FIG. 16C), or after theelement formation layer 1919 is separated from the substrate 1901 (at astage shown in FIG. 17A), or after the element formation layer 1919 issealed with the first sheet material and the second sheet material (at astage shown in FIG. 17B). An example in which the element formationlayer 1919 and the battery are formed such that they are connected toeach other is described below with reference to FIGS. 18A and 18B andFIGS. 19A and 19B.

In FIG. 16B, conductive films 1931 a and 1931 b, which are electricallyconnected to the conductive films 1915 a and 1915 b, respectively, areformed at the same time as the conductive films 1917 a and 1917 b whichserve as antennas. Next, the insulating film 1918 is formed so as tocover the conductive films 1917 a and 1917 b and the conductive films1931 a and 1931 b. Then, openings 1932 a and 1932 b are formed so as toexpose surfaces of the conductive films 1931 a and 1931 b. Subsequently,as shown in FIG. 18A, after openings are formed in the element formationlayer 1919 by laser light irradiation, the first sheet material 1920 isattached to one surface of the element formation layer 1919 (the surfacewhere the insulating film 1918 is exposed); and then, the elementformation layer 1919 is separated from the substrate 1901.

Next, as shown in FIG. 18B, the second sheet material 1921 is attachedto the other surface (a surface exposed by separation) of the elementformation layer 1919, and the element formation layer 1919 is thenseparated from the first sheet material 1920. Accordingly, in thisembodiment mode, a sheet material with weak adhesion is used as thefirst sheet material 1920. Then, conductive films 1934 a and 1934 b,which are electrically connected to the conductive films 1931 a and 1931b, respectively, through the openings 1932 a and 1932 b, are selectivelyformed.

The conductive films 1934 a and 1934 b are formed of a conductivematerial, using a CVD method, a sputtering method, a printing methodsuch as a screen printing method or a gravure printing method, a dropletdischarge method, a dispensing method, a plating method, or the like.The conductive material is any of the elements aluminum (Al), titanium(Ti), silver (Ag), copper (Cu), gold (Au), platinum (Pt), nickel (Ni),palladium (Pd), tantalum (Ta), and molybdenum (Mo), or an alloy materialor a compound material containing one of the above-mentioned elements asits main constituent, and has a single-layer structure or astacked-layer structure.

Note that in this embodiment mode, an example in which the conductivefilms 1934 a and 1934 b are formed after the element formation layer1919 is separated from the substrate 1901 is described; however, theelement formation layer 1919 may be separated from the substrate 1901after the conductive films 1934 a and 1934 b are formed.

Next, as shown in FIG. 19A, in the case where a plurality of elements isformed over the substrate, the element formation layer 1919 is separatedinto separate elements. A laser irradiation apparatus, a dicingapparatus, a scribing apparatus, or the like can be used for theseparation. Here, the plurality of elements formed over one substrateare separated from one another by laser light irradiation.

Next, as shown in FIG. 19B, the separated element is electricallyconnected to connecting terminals of the battery. Here, conductive films1936 a and 1936 b provided on the substrate 1935 which serve asconnecting terminals of the battery are connected to the conductivefilms 1934 a and 1934 b provided over the element formation layer 1919,respectively. A case is shown in which the conductive film 1934 a andthe conductive film 1936 a, or the conductive film 1934 b and theconductive film 1936 b, are pressure-bonded to each other with amaterial having an adhesive property such as an anisotropic conductivefilm (ACF) or an anisotropic conductive paste (ACP) interposedtherebetween, so that they are electrically connected to each other. Anexample is shown in which conductive particles 1938 contained in a resin1937 having an adhesive property are used for connection. Alternatively,connection can be performed using a conductive adhesive agent such as asilver paste, a copper paste, or a carbon paste, or using solderbonding, or the like.

In a case where the battery is larger than the element, by forming aplurality of elements over one substrate, as shown in FIGS. 18A and 18Band FIGS. 19A and 19B, separating the elements, then connecting theelements to the battery, the number of elements which can be formed overone substrate can be increased. Accordingly, a semiconductor device canbe formed at low cost.

According to the above-described steps, a semiconductor device can bemanufactured. Note that in this embodiment mode, a step in whichseparation is performed after forming elements such as thin filmtransistors over the substrate was described; however, the substrateover which elements are formed may be used as a product withoutperforming separation. Further, when elements such as thin filmtransistors are provided over a glass substrate, and the glass substrateis then polished on the side opposite to the surface over which theelements are provided; or when a semiconductor substrate such as Si orthe like is used and MOS transistors are formed, and the semiconductorsubstrate is then polished, thinning and miniaturization of asemiconductor device can be achieved.

Note that the method of manufacturing a semiconductor device describedin this embodiment mode can be applied to methods of manufacturingwireless power storage devices described in other embodiment modes inthis specification.

Embodiment Mode 5

In this embodiment, uses of an RFID tag, which is an example of a usagemode of a semiconductor device which is capable of transmitting andreceiving information wirelessly which was described in Embodiment Mode3, will be described. An RFID tag can be included in, for example,bills, coins, securities, bearer bonds, documents (such as driver'slicenses or resident's cards), packaging containers (such as wrappingpaper or bottles), storage media (such as DVD software or video tapes),vehicles (such as bicycles), personal belongings (such as bags orglasses), foods, plants, animals, human bodies, clothing, everydayarticles, products such as electronic appliances, identification tags onluggage, and the like. An RFID tag can be used as a so-called ID label,ID tag, or ID card. An electronic appliance refers to a liquid crystaldisplay device, an EL display device, a television set (also calledsimply a television, a TV receiver, or a television receiver), a mobilephone, or the like. Below, applications of the invention and examples ofproducts which include an application of the invention are describedwith reference to FIGS. 20A to 20E.

FIG. 20A shows examples of completed RFID tags relating to theinvention. A plurality of ID labels 3003 each including an RFID tag 3002are formed on a label board 3001 (separate paper). The ID labels 3003are stored in a box 3004. Further, on the ID label 3003, there isinformation about a product or service (a product name, a brand, atrademark, a trademark owner, a seller, a manufacturer, or the like).Meanwhile, an ID number that is unique to the product (or the type ofproduct) is assigned to the included RFID tag, so that forgery,infringement of intellectual property rights such as patent rights andtrademark rights, and illegal behavior such as unfair competition caneasily be detected. In addition, a large amount of information thatcannot be clearly shown on a container of the product or the label (forexample, production area, selling area, quality, raw materials,efficacy, use, quantity, shape, price, production method, method of use,time of production, time of use, expiration date, instructions for theproduct, information about the intellectual property of the product, orthe like) can be input to the RFID tag so that a client or a consumercan access the information using a simple reader. Further, the RFID tagis structured such that the producer of a product can easily rewrite orerase, for example, the information, but a client or a consumer cannot.Note that a structure where the RFID tag has a display portion and candisplay the information may be employed.

FIG. 20B shows a label-shaped RFID tag 3011 which includes an RFID tag3012. By providing a product with the RFID tag 3011, management of theproduct can be simplified. For example, in a case where the product isstolen, the product can be traced, so the culprit can be identifiedquickly. Thus, by providing the RFID tag, products that are superior inso-called traceability can be distributed.

FIG. 20C shows an example of a completed ID card 3021 including an RFIDtag 3022. The ID card 3021 may be any kind of card: a cash card, acredit card, a prepaid card, an electronic ticket, electronic money, atelephone card, a membership card, or the like. Further, a structure inwhich a display portion is provided on a surface of the ID card 3021 andvarious information is displayed may be employed.

FIG. 20D shows a completed bearer bond 3031. An RFID tag 3032 isembedded in the bearer bond 3031 and is protected by a resin which formsthe periphery of the RFID tag. Here, the resin is filled with a filler.The bearer bond 3031 can be formed in the same manner as an RFID tag ofthe invention. Note that the aforementioned bearer bond may be a stamp,a ticket, an admission ticket, a merchandise coupon, a book coupon, astationery coupon, a beer coupon, a rice coupon, various types of giftcoupon, various types of service coupon, or the like. Needless to say,the bearer bond is not limited thereto. Further, when the RFID tag 3032of the invention is provided in bills, coins, securities, bearer bonds,documents, or the like, an authentication function can be provided, andby using the authentication function, forgery can be prevented.

FIG. 20E shows a book 3043 to which an ID label 3041 which includes anRFID tag 3042 is attached. The RFID tag 3042 of the invention is firmlyattached in or on goods by being attached to a surface or embedded, forexample. As shown in FIG. 20E, the RFID tag 3042 can be embedded in thepaper of a book, or embedded in an organic resin of a package. Becausethe RFID tag 3042 of the invention can be small, thin, and lightweight,it can be firmly attached to or in goods without spoiling their design.

Further, the efficiency of a system such as an inspection system can beimproved by providing the RFID tag of the invention in, for example,packaging containers, storage media, personal belongings, foods,clothing, everyday articles, electronic appliances, or the like.Furthermore, by providing the RFID tag on or in a vehicle, counterfeitand theft can be prevented. Living things such as animals can be easilyidentified by implanting the individual living things with RFID tags.For example, year of birth, sex, breed, and the like can be easilydiscerned by implanting wireless tags in living things such as domesticanimals.

FIGS. 21A and 21B show a book 2701 and a plastic bottle 2702 to which IDlabels 2502 which include an RFID tag of the invention are attached.Because the RFID tag that is used in the present invention is very thin,when the ID label is mounted on goods such as the book, function anddesign are not spoiled. Further, in the case of a non-contact type thinfilm integrated circuit device, an antenna and a chip can be formed overthe same substrate and the non-contact type thin film integrated circuitdevice can be directly transferred to a product which has a curvedsurface easily.

FIG. 21C shows the ID label 2502 which includes the RFID tag directlyattached to fresh food, which is a piece of fruit 2705. Further, FIG.21D shows examples of fresh food, vegetables 2704, wrapped in a wrappingfilm 2703. Note that in the case of attaching a chip 2501 to a product,it is possible that the chip 2501 might be taken off; however, in thecase of wrapping the product with the packaging film 2703, it isdifficult to take off the packaging film 2703. Therefore, to someextent, there is the advantage of a crime prevention measure. Note thatthe wireless power storage device of the invention can be applied to allkinds of products besides the above-mentioned products.

Further, a semiconductor device provided with a wireless power storagedevice of the invention can be provided with the sensor portion 190 asshown in FIG. 11 of Embodiment Mode 3, and can detect variousinformation. Therefore, by having a person, an animal, or the like carrythe semiconductor device mounted with the sensor portion with them,various information such as biological information and information on astate of health can be evaluated semipermanently, regardless oflocation. Below, specific examples of usage modes of a semiconductordevice provided with a wireless power storage device will be describedwith reference to the drawings.

A semiconductor device 552 in which a sensor portion is provided with anelement which detects temperature is embedded in an animal 551, and afeedbox or the like provided near the animal 551 is provided with areader/writer 553 (FIG. 22A). Then, the sensor portion is operatedintermittently and evaluated information is stored in the semiconductordevice 552. Subsequently, by using the reader/writer 553 to periodicallyread information, such as information about body temperature, about theanimal 551 which is detected by the semiconductor device 552, the stateof health of the animal 551 can be monitored and managed. In this case,charging of a battery provided in the semiconductor device 552 may beperformed using electromagnetic waves from the reader/writer 553.

Further, foods 555 are provided with semiconductor devices 556 in whichsensor portions include elements which detect gas components such asgas, and wrapping paper or a showcase is provided with a reader/writer557 (FIG. 22B). Then, the sensor portion is operated intermittently andevaluated information is stored in the semiconductor device 556.Subsequently, by using the reader/writer 557 to periodically readinformation which is detected by the semiconductor device 556, thefreshness of the foods 555 can be managed.

Further, a plant 561 is provided with a semiconductor device 562 inwhich a sensor portion includes an element which detects light, and apot of the plant 561 or the like is provided with a reader/writer 563(FIG. 22C). Then, the sensor portion is operated intermittently andevaluated information is stored in the semiconductor device 562.Subsequently, by using the reader/writer 563 to periodically readinformation which is detected by the semiconductor device 562,information about hours of sunshine can be obtained, and information onwhen the plant will bloom and be shipped can be predicted accurately. Inparticular, in the semiconductor device 562 which includes an elementwhich detects light, when a solar cell is also provided, a batteryprovided in the semiconductor device 562 can be charged using light fromoutside as well as a power supply which employs electromagnetic wavesfrom the reader/writer 563.

Further, an arm of a human body is provided with a semiconductor device565 in which a sensor portion includes an element which detectspressure, by attaching or embedding the semiconductor device 565 (FIG.22D). Then, the sensor portion is operated intermittently and evaluatedinformation is stored in the semiconductor device 565. Subsequently,when a reader/writer is used to read information detected by thesemiconductor device 565, information about blood pressure, pulse, andthe like can be obtained.

A semiconductor device mounted with a wireless power storage device ofthe invention can be applied to all kinds of products besides theabove-mentioned products. Note that in this embodiment mode, uses of anRFID tag which is an example of a usage mode of a semiconductor devicewere described; however, the invention is not limited to this. Wirelesspower storage devices described in previous embodiment modes can beincluded in the above-mentioned electronic devices. In such cases, aselectrical power which operates the electronic device, electrical powerobtained wirelessly from outside by the wireless power storage devicecan be used.

Embodiment Mode 6

In this embodiment mode, an example of a battery provided in a wirelesspower storage device of the invention will be described. In thisembodiment mode, a battery which supplies electrical power to the loadby discharging most, for example, 80 percent or more, of the electricalpower charged to the battery, through discharging a certainpredetermined number of times, preferably two times or less, isemployed. That is, a battery is used in which the amount of electricalpower discharged per unit time is greater, preferably twice as much ormore, more preferably five times as much or more, than the amount ofelectrical power charged per unit time. The battery has a structure suchthat the battery is not discharged until the battery has been charged to80 percent or more of its capacity.

When such a battery is employed, a large amount of electrical power canbe supplied even when an electromagnetic wave used in charging thebattery is weak. Further, when the battery has a capacity such that theelectrical power necessary for the load to operate is discharged only afew times, the battery size can be reduced and the wireless powerstorage device can be made smaller and lighter.

Note that the battery structure described in this embodiment mode can becombined with structures of wireless power storage devices described inother embodiment modes in this specification.

The present application is based on Japanese priority application No.2006-266513 filed on 29 Sep. 2006 with the Japanese Patent Office, theentire contents of which are hereby incorporated by reference.

1. A wireless power storage device comprising: an antenna circuit; a rectifier circuit; a battery electrically connected to the antenna circuit through the rectifier circuit; and a discharge control circuit comprising a regulator and a switch, wherein the battery is electrically connected to a load portion through the discharge control circuit, wherein the discharge control circuit is configured to control the supply of electrical power stored in the battery to the load portion by turning on the switch when a voltage level of the battery is equal to or higher than a first threshold level and by turning off the switch when the voltage level of the battery is equal to or lower than a second threshold level, and wherein the first threshold level is higher than the second threshold level.
 2. The wireless power storage device according to claim 1, wherein the battery is a capacitor.
 3. The wireless power storage device according to claim 1, wherein the battery is a secondary cell.
 4. The wireless power storage device according to claim 1, further comprising a charge control circuit.
 5. The wireless power storage device according to claim 1, wherein the load portion is a signal processing circuit.
 6. The wireless power storage device according to claim 1, wherein an amount of electrical power discharged from the battery per unit time is twice as much or more than an amount of electrical power charged to the battery per unit time.
 7. The wireless power storage device according to claim 1, wherein the regulator is electrically connected to the battery through the switch.
 8. The wireless power storage device according to claim 1, wherein the discharge control circuit further comprises a Schmitt trigger.
 9. The wireless power storage device according to claim 1, wherein each of the rectifier circuit and the discharge control circuit comprises a transistor including a semiconductor layer.
 10. The wireless power storage device according to claim 1, wherein each of the rectifier circuit and the discharge control circuit comprises a thin film transistor.
 11. A semiconductor device comprising: a first antenna circuit; a power supply portion electrically connected to the first antenna circuit wherein the power supply portion comprises: a rectifier circuit; a battery electrically connected to the first antenna circuit through the rectifier circuit; and a discharge control circuit comprising a regulator and a switch; and a load portion electrically connected to the battery through the discharge control circuit, wherein the first antenna circuit is electrically connected to the battery through the rectifier circuit, wherein the discharge control circuit is configured to control the supply of electrical power stored in the battery to the load portion by turning on the switch when a voltage level of the battery is equal to or higher than a first threshold level and by turning off the switch when the voltage level of the battery is equal to or lower than a second threshold level, and wherein the first threshold level is higher than the second threshold level.
 12. The semiconductor device according to claim 11, wherein the battery is a capacitor.
 13. The semiconductor device according to claim 11, wherein the battery is a secondary cell.
 14. The semiconductor device according to claim 11, further comprising a charge control circuit.
 15. The semiconductor device according to claim 11, wherein the load portion is a signal processing circuit.
 16. The semiconductor device according to claim 11, further comprising a second antenna circuit, wherein the first antenna circuit receives an electromagnetic wave having a different frequency to an electromagnetic wave which is received by the second antenna circuit.
 17. The semiconductor device according to claim 11, wherein an amount of electrical power discharged from the battery per unit time is twice as much or more than an amount of electrical power charged to the battery per unit time.
 18. The semiconductor device according to claim 11, wherein the regulator is electrically connected to the battery through the switch.
 19. The semiconductor device according to claim 11, wherein the discharge control circuit further comprises a Schmitt trigger.
 20. The semiconductor device according to claim 11, wherein each of the rectifier circuit and the discharge control circuit comprises a transistor including a semiconductor layer.
 21. The semiconductor device according to claim 11, wherein each of the rectifier circuit and the discharge control circuit comprises a thin film transistor.
 22. A semiconductor device comprising: a first antenna circuit; a power supply portion electrically connected to the first antenna circuit wherein the power supply portion comprises: a rectifier circuit; a battery electrically connected to the first antenna circuit through the rectifier circuit; and a discharge control circuit comprising a regulator and a switch; and a sensor portion electrically connected to the battery through the discharge control circuit, wherein the first antenna circuit is electrically connected to the battery through the rectifier circuit, wherein the discharge control circuit is configured to control the supply of electrical power stored in the battery to the sensor portion by turning on the switch when a voltage level of the battery is equal to or higher than a first threshold level and by turning off the switch when the voltage level of the battery is equal to or lower than a second threshold level, and wherein the first threshold level is higher than the second threshold level.
 23. The semiconductor device according to claim 22, wherein the battery is a capacitor.
 24. The semiconductor device according to claim 22, wherein the battery is a secondary cell.
 25. The semiconductor device according to claim 22, further comprising a charge control circuit.
 26. The semiconductor device according to claim 22, further comprising a second antenna circuit, wherein the first antenna circuit receives an electromagnetic wave having a different frequency to an electromagnetic wave which is received by the second antenna circuit.
 27. The semiconductor device according to claim 22, wherein an amount of electrical power discharged from the battery per unit time is twice as much or more than an amount of electrical power charged to the battery per unit time.
 28. The semiconductor device according to claim 22, wherein the regulator is electrically connected to the battery through the switch.
 29. The semiconductor device according to claim 22, wherein the discharge control circuit further comprises a Schmitt trigger.
 30. The semiconductor device according to claim 22, wherein each of the rectifier circuit and the discharge control circuit comprises a transistor including a semiconductor layer.
 31. The semiconductor device according to claim 22, wherein each of the rectifier circuit and the discharge control circuit comprises a thin film transistor.
 32. A method for operating a wireless power storage device, comprising the steps of: receiving an electromagnetic wave by an antenna circuit; charging a battery with electrical power of the electromagnetic wave through a rectifier circuit; and discharging the battery by supplying electrical power stored in the battery to a load portion through a discharge control circuit including a regulator and a switch, wherein the supply of the electrical power is controlled by turning on the switch when a voltage level of the battery is equal to or higher than a first threshold level and by turning off the switch when the voltage level of the battery is equal to or lower than a second threshold level.
 33. The method for operating a wireless power storage device according to claim 32, wherein the battery is a capacitor.
 34. The method for operating a wireless power storage device according to claim 32, wherein the battery is a secondary cell.
 35. The method for operating a wireless power storage device according to claim 32, wherein the charge of the battery is controlled by a charge control circuit.
 36. The method for operating a wireless power storage device according to claim 32, wherein the load portion is a signal processing circuit.
 37. The method for operating a wireless power storage device according to claim 32, wherein an amount of electrical power discharged from the battery per unit time is twice as much or more than an amount of electrical power charged to the battery per unit time.
 38. The method for operating a wireless power storage device according to claim 32, wherein the regulator is electrically connected to the battery through the switch.
 39. The method for operating a wireless power storage device according to claim 32, wherein the discharge control circuit further comprises a Schmitt trigger.
 40. The method for operating a wireless power storage device according to claim 32, wherein each of the rectifier circuit and the discharge control circuit comprises a transistor including a semiconductor layer.
 41. The method for operating a wireless power storage device according to claim 32, wherein each of the rectifier circuit and the discharge control circuit comprises a thin film transistor. 